The Giant Geode of Pulpi is a rock formation located in the Mina Rica, near the neighbourhood of Pilar de Jaravia in the Sierra del Aguilon. It is also called the Geoda de Jaravia because of its location. It was discovered by the Mineralogist Group of Madrid in December 1999.
This formation, which is almost sixty metres underground, is egg-shaped and measures 8 metres long by almost 2 metres wide. It is believed to be the largest geode of its kind in Europe and the second largest in the world.
The geological analyses indicate that this cave was formed 6 million years ago, during an event known as the Messinian Salinity Crisis. This is part of the geological history of the Mediterranean Sea in which the evaporation of sea water caused a massive accumulation of salts and gypsum under the ground.
This geological treasure has become a worldwide phenomenon due to the dimensions, transparency and perfection of its selenite crystals that resemble enormous ice formations that cover the interior of the cave.
The Pulpi Geode is funnel-shaped, and L-shaped at its narrowest part, and its formations have a hardness of 2 on the Mohs scale. In some of the crystals, one can observe the impurities derived from the iron and manganese that accumulated during the geode's growth stages.
It is believed that the Sierra de Aguilon has been explored since prehistory by people in search of metals, especially silver. The deposits found in Las Herrerias and Sierra Almagrera stimulated the economy of these lands, however, it was not until the middle of the 19th century when mining and industrial development of the province of Almeria began.
At that time, large companies invested in the mechanisation of both the production and transportation of ore. The movement of materials was expedited by overhead cables and by rail, then exported by sea to England and Germany.
The success of operations in the Sierra Almagrera gave rise to further exploration of the Pilar de Jaravia mines located in Pulpi, where conditions were similar. As a result, the mine provided the largest production in the region for a long time, and even in the 60s, up to 6 kilograms of silver per tonne of ore were extracted. Also, at the Rica Mine, there were attempts to extract iron ore, dolomite, limestone and even cinnabar, but the expiration of concessions led to closing the mine and abandoning the facilities.
As a result of the mining activity of that time, there are some vestiges of old delapidated mines that have remained intact and are accessible to researchers. Other mines have disappeared due to extreme delapidation which has caused a great loss to the historical heritage of the region.
According to mineralogical investigations that have been carried out in Pilar de Jaravia, the most remarkable type of deposit that has been found is gypsum, in very large quantities, and in many unusual crystallised formations. There is an absence of other minerals, however, these rounded surface cavities that were created by hydrothermal processes, contain abundant inclusions of sheet material with yellow, orange and brown tints, which are the product of iron oxide and other clay materials.
During an initial exploration of the area, what looked like a wide shallow well with a patch of mineral deposit that showed a small cavity through which broken glass protruded, turned out to be the Giant Geode of Pulpi!
While the researchers attempted to establish the conservation parameters of the Geode, government agencies ordered the closure of the mine with rocks and debris, which blocked off level 14 of the Mina Rica.
As protection of this unique natural resource is vital for its conservation, the Chamber of Deputation of the Province of Almeria and the City Hall of Pulpi signed an agreement to provide funding of 500,000 euros for preservation and maintenance work. When the necessary works are completed, this will enable people to visit to the monument from the year 2019. Tourists and locals will have access to the site where they can explore the 350 metres of galleries within this majestic geological treasure, as well as a large part of the Mina Rica.